jasons and any one else, here is a statement direct from the website you posted, from the author.
What is ZDP?
* Zinc-dialkyl-dithiophosphate
* Abbreviated as ZDP or ZDDP, which ever you prefer
* Forms a polyphosphate tribo film separating the cam lobe from the lifter
* Prevents adhesion of the lobe to the lifter, and break-in scuffing
* Also protects the surfaces from abrasive and corrosive wear
ZDP: the Miracle Drug
* The truly amazing thing is that the ZDP forms this polyphosphate tribo film where it is needed
* A thin film, measured in nanometers, is formed on surfaces as the result of contact pressure and sliding speed
* You only need enough active ZDP to form the film initially and replenish it as it wears away
How Much ZDP is Enough?
* It does not take much ZDP to form these thin films on the wear surfaces
* The ZDP does not “waste itself” forming films on all the surfaces of the crankcase
* ILSAC GF-4/API SM oils contain much more ashless antioxidants, which allow the ZDP to “save itself” for acting as an anti-wear agent instead of an antioxidant
Summary
* The preponderance of dynamometer and vehicle testing indicates that the current level of ZDP in modern passenger car motor oils is more than enough to protect older engines
* If you want to install a high-performance camshaft, invest in a roller-follower cam and lifters
i am saying that the zddp levels are cut way down from past levels. most of us run aftermarket "aggresive cams", we need the zddp to protect the cam and lifters.
modern oil will work fine on a perfectly stock older motor that is already broke in.
try to break a cam in with modern oil and it is a crap shoot. the higher amounts of zddp is surely needed here. tom
